In the early days of organ transplantation, all cadaveric (non-living) organ donors were pronounced dead by loss of heart function or “cardiac death” criteria. However, in the late 1960's and early 1970's “brain death” criteria were developed that allowed organs to be harvested from donors who's hearts were still beating but who had been pronounced dead based on the irreversible cessation of all brain activity. Additionally, it was learned that organ transplantation was more successful in cases where the donor's respiration and circulation were supported by artificial means (e.g., the use of mechanical ventilation and the administration of pharmacologic or mechanical support of cardiac activity) after brain death had occurred until the organs could be removed for transplantation. This “beating heart donor” technique enables oxygenated blood to continue to flow through the organs until immediately before they are harvested from the donor, thereby enhancing the organs' viability.
Every day, approximately ten people die in the United States while awaiting an organ transplant, simply because suitable donor organs are not available for them in time. Various approaches have been proposed for making transplantable organs more readily available to patients in need of transplants. For example, research is underway to develop genetically or immunologically modified animals who's organs may be suitable for xenotransplantation (i.e., transplantation of an organ or tissue from one species of animal into another species of animal) in humans. However, it remains uncertain as to whether xenotransplantation research will ultimately give rise to universally useable organs of all needed types and even if the current research is successful, the potential clinical implementation of xenotransplantation techniques remains many years away. Another approach has been to obtain some types of organs from human cadaveric donors who have been declared dead by traditional cardiac death criteria as opposed to brain death criteria. However, a number of important transplantable organs (e.g., hearts) can not typically be harvested from cadaveric donors more than just a few minutes after the cardiac death has occurred because the viability of the organ is lost.
On Jan. 6,2001 The United Network for Organ Sharing (UNOS) national patient waiting list for organ transplant included the following:
Type of TransplantPatients Waiting for Transplantkidney transplant47,689liver transplant16,815pancreas transplant1,033pancreas islet cell transplant178kidney-pancreas transplant2,457intestine transplant147heart transplant4,152heart-lung transplant206lung transplant3,676*Total Patients Total*73,989
However, because of the shortage of suitable donor organs, the number of organ transplants that will actually be performed during the year 2001 is likely to be substantially lower than the number of patients on the waiting list. During the year 2000, the number of transplants actually performed in the United States were as follows:
Type of TransplantNumberkidney alone transplants 13,290(5,227 were living donors)liver transplants4,934pancreas alone transplants436kidney-pancreas transplants914intestine transplants79heart transplants2,197heart-lung transplants48lung transplants956Total22,854
Apart from the fact that the pool of potential organ donors is relatively small compared to the demand for transplantable organs, the shortage of organs is further exacerbated by the fact that sometimes, even after a potential donors family has agreed to organ donation, that donor's organs are lost because the donors cardiac activity can not be maintained for sufficient time to allow the necessary testing to establish and certify brain-death and to arrange for the arrival of the team of surgeons who are trained to remove the desired organ(s) from the donor's body. In view of these facts, there remains a need in the art for the development of new techniques to facilitate the harvesting of viable organs for transplantation so that more organs may be made available.